The purpose in this study was inventing an instructional method to develop “scientific competencies” through a unit for junior high school students. And the instructional method focus on “the ability to using scientific evidence” in “scientific competencies”. In this method, students will do the following four leaning activities in the unit of “Changes in biological and animal life”. First, they will lead conclusion which based on scientific evidence. Second, they will evaluate the conclusion of others and self. In order to investigate effectiveness of the method, we conducted a class which 41 junior high school students. Based on their writings on questionnaires and worksheets for class, we conclude that our method can improve their ability to evaluate the conclusion of others and self, which is a part of “the ability to using scientific evidence”.